Light emitting diode

ABSTRACT

A light emitting diode, the light emitting diode including: a first semiconductor layer, an active layer, a second semiconductor layer, wherein a surface of the second semiconductor layer defines a first area; a metallic plasma generating layer; a first electrode; a second electrode; wherein the metallic plasma generating layer includes a plurality of three-dimensional nanostructures, the three-dimensional nanostructure includes a first rectangular structure, a second rectangular structure, and a triangular prism structure, the first rectangular structure, the second rectangular structure, and the triangular prism structure are stacked, the width of the triangular prism structure is equal to the width of the second rectangular structure, and is greater than the width of the first rectangular structure, the first rectangular structure is a metal layer, and the triangular prism structure is a metal layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending applications entitled, “SOLARCELL”, U.S. patent application Ser. No. 15/990,929, concurrently filedon May 29, 2018, “METHOD OF DETECTING SINGLE MOLECULES”, U.S. patentapplication Ser. No. 15/990,933, concurrently filed on May 29, 2018.

FIELD

The subject matter herein generally relates to a light emitting diode.

BACKGROUND

The light emitting diodes are widely used as the light sources in largescreen color display systems, automotive lightening, traffic lights,multimedia displays, optical communication systems, and so on. Since thebrightness of light emitting diode is limited, the light emitting diodescannot be applied to indoor lighting on a large scale. So it isnecessary to increase the luminous efficiency of light emitting diodes.However, the refractive index of the semiconductor materials is high,only a small part of light generated by the light emitting diodes canradiate into the outside, and most of the light is absorbed by theelectrode or the light-emitting layer. Therefore, the luminousefficiency of light emitting diodes is lower.

What is needed, therefore, is to provide a light emitting diode forsolving the problem discussed above.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with referencesto the following drawings. The components in the drawings are notnecessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views. Implementations of the present technologywill now be described, by way of example only, with reference to theattached figures, wherein:

FIG. 1 is a structural schematic view of one embodiment of a lightemitting diode.

FIG. 2 is a sectional view of the light emitting diode of FIG. 1.

FIG. 3 is a structural schematic view of one embodiment of a metallicplasma generating layer having different patterns.

FIG. 4 is an exploded view of one embodiment of the three-dimensionalnanostructures.

FIG. 5 is a flow chart of one embodiment of a method for making a lightemitting diode.

FIG. 6 is a flow chart of one embodiment of a method for the metallicplasma generating layer.

FIG. 7 is a low magnification Scanning Electron Microscope (SEM) imageof the metallic plasma generating layer.

FIG. 8 is a high magnification Scanning Electron Microscope (SEM) imageof the metallic plasma generating layer.

FIG. 9 is a structural schematic view of one embodiment of a lightemitting diode.

FIG. 10 is a structural schematic view of one embodiment of a lightemitting diode.

FIG. 11 is a structural schematic view of one embodiment of a lightemitting diode.

FIG. 12 is a sectional view of the light emitting diode of FIG. 11.

FIG. 13 is a structural schematic view of one embodiment of a lightemitting diode.

FIG. 14 is a sectional view of the light emitting diode of FIG. 13.

FIG. 15 is a structural schematic view of one embodiment of the metallicplasma generating layer and the second metal layer.

FIG. 16 is a structural schematic view of one embodiment of a lightemitting diode.

DETAILED DESCRIPTION

It will be appreciated that for simplicity and clarity of illustration,where appropriate, reference numerals have been repeated among thedifferent figures to indicate corresponding or analogous elements. Inaddition, numerous specific details are set forth in order to provide athorough understanding of the embodiments described herein. However, itwill be understood by those of ordinary skill in the art that theembodiments described herein can be practiced without these specificdetails. In other instances, methods, procedures, and components havenot been described in detail so as not to obscure the related relevantfeature being described. The drawings are not necessarily to scale, andthe proportions of certain parts may be exaggerated to better illustratedetails and features. The description is not to be considered aslimiting the scope of the embodiments described herein.

Several definitions that apply throughout this invention will now bepresented.

The connection can be such that the objects are permanently connected orreleasably connected. The term “substantially” is defined to beessentially conforming to the particular dimension, shape or other wordthat substantially modifies, such that the component need not be exact.The term “comprising” means “including, but not necessarily limited to”;it specifically indicates open-ended inclusion or membership in aso-described combination, group, series and the like. It should be notedthat references to “an” or “one” embodiment in this disclosure are notnecessarily to the same embodiment, and such references mean at leastone.

Referring to FIG. 1 and FIG. 2, an embodiment of a light emitting diode10 comprises a first semiconductor layer 120, an active layer 130, asecond semiconductor layer 140, a metallic plasma generating layer 160,a first electrode 180, and a second electrode 182. The firstsemiconductor layer 120, the active layer 130, and the secondsemiconductor layer 140 are stacked in that order. A surface of thesecond semiconductor layer 140 defines a first area 1402 and a secondarea 1404. The metallic plasma generating layer 160 is located on thefirst area 1402. The first electrode 180 is electrically connected tothe first semiconductor layer 120. The second electrode 182 is locatedon the second area 1404 and electrically connected to the secondsemiconductor layer 140. The metallic plasma generating layer 160includes a plurality of three-dimensional nanostructures 161. Thethree-dimensional nanostructure 161 is a pine shaped structure. Thefirst semiconductor layer 120, the active layer 130, and the secondsemiconductor layer 140 cooperatively constitute a source layer of thelight emitting diode 10.

A thickness of the first semiconductor layer 120 can be in a range fromabout 1 micrometer to about 15 micrometers. The first semiconductorlayer 120 can be a doped semiconductor layer. The doped semiconductorlayer can be an N-type semiconductor layer or a P-type semiconductorlayer. A material of the N-type semiconductor layer can be at least oneof N-type GaN, N-type GaAs, and N-type cupric phosphide. A material ofthe P-type semiconductor layer can be at least one of P-type GaN, P-typeGaAs, and P-type cupric phosphide. In one embodiment, the material ofthe first semiconductor layer 120 is the N-type GaN doped with Sielement, and the thickness of the first semiconductor layer 120 is about1460 nanometers.

The active layer 130 is a photon excitation layer to provide a locationfor the combination of the electrons and holes. Photons are produced inthe active layer 130 when the electrons and holes combined. The activelayer 130 can be one of a single layer quantum well film or multilayerquantum well film. A material of the quantum well film can be at leastone of GaInN, AlGaInN, GaAs, GaAlAs, GaInP, InAsP, and InGaAs. Athickness of the active layer 130 can be in a range from 0.01micrometers to 0.6 micrometers. In one embodiment, the material of theactive layer 130 is a composition of InGaN and GaN, and the thickness ofthe active layer 130 is about 10 nanometers.

The second semiconductor layer 140 can be the N-type semiconductor layeror the P-type semiconductor layer, and the type of the firstsemiconductor layer 120 and the second semiconductor layer 140 isdifferent to form a PN conjunction. The second semiconductor layer 140is disposed between the metallic plasma generating layer 160 and theactive layer 130. A thickness of the second semiconductor layer 140 isin a range from 5 nanometers to 30 nanometers. furthermore, thethickness of the second semiconductor layer 140 can be in a range from10 nanometers to 20 nanometers. furthermore, the thickness of the secondsemiconductor layer 140 can be 12 nanometers, 18 nanometers, or 22nanometers. In one embodiment, the second semiconductor layer 140 is theP-type GaN doped with Mg element, and the thickness of the secondsemiconductor layer 140 is 10 nanometers.

The metallic plasma generating layer 160 can generate a metallic plasmaunder an action of photons. A refractive index of a material of themetallic plasma generating layer is a complex number including a realpart and an imaginary part, and the imaginary part is greater than zeroor smaller than zero. In addition, a dielectric constant of the materialof the metallic plasma generating layer is a second complex numberincluding a second real part and a second imaginary part, and the realpart is a negative number. The material of the metallic plasmagenerating layer 160 can be selected according to wavelengths of lightgenerated in the active layer 130. In one embodiment, the material ofthe metallic plasma generating layer 160 is a metallic material selectedfrom an elemental metal or an alloy, such as gold, silver, aluminum,copper, gold-silver alloy, gold-aluminum alloy, or silver-aluminumalloy. The metallic plasma generating layer of the silver is good for anextraction of light with a short wavelength. In one embodiment, thematerial of the metallic plasma generating layer is a metal matrixcomposite, such as a cermet. The metallic plasma generating layer of themetal matrix composite is good for an extraction of light with a longwavelength. The cermet is a composition of the metallic material and adielectric material. The dielectric material is a non-conductivematerial, such as silicon dioxide, silicon, and a ceramic. An amountratio between the metallic material and the dielectric material isselected to ensure that the metallic plasma generating layer can producethe metallic plasma.

The metallic plasma generating layer 160 includes a plurality ofthree-dimensional nanostructures 161, and the plurality ofthree-dimensional nanostructures 161 are arranged side by side andextend along a same direction. The plurality of three-dimensionalnanostructures 161 are arranged periodically to improve the couplingefficiency of plasma and light and the luminous intensity. In oneembodiment, the plurality of three-dimensional nanostructures 161consist of two metal layers with surface plasmons. The surface plasmonresonance characteristics of three-dimensional nanostructures canmanipulate light intensity and light conduction in the nanoscale toimprove the efficiency of generating plasma.

The plurality of three-dimensional nanostructures 161 can be arrangedside by side and extend along a straight line, a fold line, or a curveline. The extending direction is parallel to a surface of the secondsemiconductor layer 140. Referring to FIG. 3, the extending directioncan be any direction which is parallel to the surface of the secondsemiconductor layer 140. The term “side by side” means that two adjacentthree-dimensional nanostructures 161 are substantially parallel witheach other along the extending direction. The distance between twoadjacent three-dimensional nanostructures 161 is in a range from 0nanometer to 200 nanometers. The plurality of three-dimensionalnanostructures 161 can be continuous or discontinuous along theextending direction. In one exemplary embodiment, the plurality ofthree-dimensional nanostructures 161 are continuous, the extendingdirection of the three-dimensional nanostructures 161 extends side byside, the three-dimensional nanostructures are strip-shaped structures,and cross sections of the three-dimensional nanostructures have the samepine shapes and the same area.

The three-dimensional nanostructures 161 are pine shaped ridges locatedon the surface of the second semiconductor layer 140. The pine shapedridges comprise a first rectangular structure 163, a second rectangularstructure 165, and a triangular prism structure 167. The firstrectangular structure 163 comprises a first top surface 1632, and thefirst top surface 1632 is away from the second semiconductor layer 140.The second rectangular structure 165 is located on the first top surface1632. The second rectangular structure 165 comprises a second topsurface 1652, and the second top surface 1652 is away from the firstrectangular structure 163. The triangular prism structure 167 is locatedon the second top surface 1652. The geometric centers of the firstrectangular structure 163, the second rectangular structure 165 and thetriangular prism structure 167 are on the same axis. The firstrectangular structure 163 and the triangular prism structure 167 areboth metal layers. The second rectangular structure 165 can isolate thefirst rectangular structure 163 and the triangular prism structure 167.

Referring to FIG. 4, the triangular prism structure 167 comprises afirst triangle surface 1670 and a second triangle surface 1672 oppositeto and substantially parallel with the first triangle surface 1670. Thesizes and shapes of the first triangle surface 1670 and the secondtriangle surface 1672 are both the same. The triangular prism structure167 further comprises a first rectangular side 1674, a secondrectangular side 1676, and a third rectangular side 1678 connected tothe first triangle surface 1670 and the second triangle surface 1672.The projection of the first triangle surface 1670 coincides with theprojection of the second triangle surface 1672. The shapes of the firsttriangle surface 1670 and the second triangle surface 1672 are bothisosceles triangle. The third rectangular side 1678 is in contact withthe second top surface 1652 of the second rectangular structure 165. Theside surface of the first rectangular structure 163 is perpendicular tothe surface of the second semiconductor layer 140. The side surface ofthe second rectangular structure 165 is perpendicular to the first topsurface 1632 of the first rectangular structure 163, thus the sidesurface of the second rectangular structure 165 is also perpendicular tothe surface of the second semiconductor layer 140.

The width d₁ of the first rectangular structure 163 is in a range of 5nanometers to 400 nanometers, the height h₁ of the first rectangularstructure 163 is in a range of 20 nanometers to 500 nanometers.Furthermore, the width d₁ of the first rectangular structure 163 can bein a range of 12 nanometers to 320 nanometers, the height h₁ of thefirst rectangular structure 163 can be in a range of 50 nanometers to200 nanometers. In one exemplary embodiment, the width d₁ of the firstrectangular structure 163 is 50 nanometers, the height h₁ of the firstrectangular structure 163 is 100 nanometers. The width d₂ of the secondrectangular structure 165 is in a range of 50 nanometers to 450nanometers, the height h₂ of the second rectangular structure 165 is ina range of 5 nanometers to 100 nanometers. Furthermore, the width d₂ ofthe second rectangular structure 165 can be in a range of 80 nanometersto 380 nanometers, the height h₂ of the second rectangular structure 165can be in a range of 5 nanometers to 60 nanometers. In one exemplaryembodiment, the width d₂ of the second rectangular structure 165 is 100nanometers, the height h₂ of the second rectangular structure 165 is 10nanometers. The width d₃ of the triangular prism structure 167 is in arange of 50 nanometers to 450 nanometers, the height h₃ of thetriangular prism structure 167 is in a range of 40 nanometers to 800nanometers. Furthermore, the width d₃ of the triangular prism structure167 can be in a range of 80 nanometers to 380 nanometers, the height h₃of the triangular prism structure 167 can be in a range of 130nanometers to 400 nanometers. In one exemplary embodiment, the width d₃of the triangular prism structure 167 is 100 nanometers, the height h₃of the triangular prism structure 167 is 200 nanometers. The width d₃ ofthe triangular prism structure 167 is the width of the third rectangularside 1678 of the triangular prism structure 167. The width d₃ of thetriangular prism structure 167 is equal to the width d₂ of the secondrectangular structure 165. The third rectangular side 1678 of thetriangular prism structure 167 is completely coincident with the secondtop surface 1652 of the second rectangular structure 165. The width d₃of the triangular prism structure 167 is greater than the width d₁ ofthe first rectangular structure 163.

Referring to FIG. 5, one embodiment of a method for making the lightemitting diode 10 includes the following steps:

S10, providing a substrate 100 with a epitaxial growth surface 1002;

S20, growing a buffer layer 110 on the epitaxial growth surface 1002,the first semiconductor layer 120 on the surface of the buffer layer110, the active layer 130 on the surface of the first semiconductorlayer 120, and the second semiconductor layer 140 on the surface of theactive layer 130 in series;

S30, forming a metallic plasma generating layer 160 on the first area1402 of the second semiconductor layer 140, wherein the surface of thesecond semiconductor layer 140 defines the first area 1402 and thesecond area 1404;

S40, removing the substrate 100 to expose a surface of the firstsemiconductor layer 120 away from the active layer 130;

S50, applying a first electrode 180 to be electrically connected to thefirst semiconductor layer 120, and a second electrode 182 electricallyconnected to the second semiconductor layer 140.

In step S10, the substrate 100 can be a transparent structure having anepitaxial growth surface 1002 used to grow the first semiconductor layer120. The epitaxial growth surface 1002 is a smooth surface. Oxygen andcarbon are removed from the surface 1002. The substrate 100 can be asingle layer structure or a multiple layer structure. If the substrate100 is a single layer structure, the substrate 100 can be asingle-crystal structure. The single-crystal structure includes acrystal plane which is used as the epitaxial growth surface 1002. Amaterial of the substrate 100 can be silicon on insulator (SOI), LiGaO₂,LiAlO₂, Al₂O₃, Si, GaAs, GaN, GaSb, InN, InP, InAs, InSb, AlP, AlAs,AlSb, AlN, GaP, SiC, SiGe, GaMnAs, GaAlAs, GaInAs, GaAlN, GaInN, AlInN,GaAsP, InGaN, AlGaInN, AlGaInP, GaP:Zn, or GaP:N. If the substrate 100is the multiple layer structure, the substrate 100 should include atleast one layer of the single-crystal structure mentioned previously.The material of the substrate 100 can be selected according to the firstsemiconductor layer 120. In one embodiment, a lattice constant andthermal expansion coefficient of the substrate 100 is similar to thefirst semiconductor layer 120 thereof to improve a quality of the firstsemiconductor layer 120. In one embodiment, the material of thesubstrate 100 is sapphire. A thickness, shape, and size of the substrate100 are arbitrary and can be selected according to need.

In step S20, the buffer layer 110, the first semiconductor layer 120,the active layer 130, and the second semiconductor layer 140 can grow bymethods of molecular beam epitaxy (MBE), chemical beam epitaxy (CBE),reduced pressure epitaxy, selective epitaxy, liquid phase depositionepitaxy (LPE), metal organic vapor phase epitaxy (MOVPE), super vacuumchemical vapor deposition, hydride vapor phase epitaxy (HVPE), metalorganic chemical vapor deposition (MOCVD), or combinations thereof. Inone embodiment, the buffer layer 110, the first semiconductor layer 120,the active layer 130, and the second semiconductor layer 140 grow by themethod of MOCVD.

A low temperature GaN layer is selected as the buffer layer 110. Anammonia gas as a nitrogen source, a hydrogen gas as a carrier gas, andtrimethyl gallium (TMGa) or triethyl gallium (TEGa) as a gallium sourceto grow the low temperature GaN layer in a reactor under a lowtemperature.

An N-type GaN layer is selected as the first semiconductor layer 120.The ammonia gas as the nitrogen source, the TMGa or TEGa as the galliumsource, silane as a Si source, and the hydrogen gas as the carrier gasto grow the N-type GaN layer in the reactor.

A process for growing the active layer 130 is substantially the same asthe process of growing the first semiconductor layer 120, except thatthe trimethyl indium is selected as an indium source.

After the active layer 130 has been grown, a magnesocene (Cp₂Mg) as amagnesium source is used to grow the second semiconductor layer 140. Thethickness of the second semiconductor layer 140 is in a range from 5nanometers to 60 nanometers by controlling a growing time period.Selectively, a thick second semiconductor layer 140 can be formed by theMOCVD method and then etched or grinded to control the thickness of thesecond semiconductor layer 140 in the range from about 5 nanometers toabout 60 nanometers.

In one embodiment, the thickness of the buffer layer 110 is 20nanometers, the thickness of the first semiconductor layer 120 is 1460nanometers, the thickness of the active layer 130 is 10 nanometers, thethickness of the second semiconductor layer 140 is 10 nanometers, andthe total thickness thereof is about 1500 nanometers.

In step S30, the surface of the second semiconductor layer 140 definesthe first area 1402 and the second area 1404. The metallic plasmagenerating layer 160 can be formed on the first area 1402 of the secondsemiconductor layer 140 using photoresist as a mask. The second area1404 is exposed. Thus, in step S50, the second electrode 182 is directlyformed on the second area 1404 and electrically connected to the secondsemiconductor layer 140.

Referring to FIG. 6, a method of making the metallic plasma generatinglayer 160 comprises:

S301, forming a first metal layer 162 on the first area 1402 of thesecond semiconductor layer 140, forming an isolation layer 164 on thefirst metal layer 162, and locating a second metal layer 166 on theisolation layer 164;

S302, placing a first mask layer 169 on the second metal layer 166,wherein the first mask layer 169 covers partial surface of the secondmetal layer 166, and other surface is exposed;

S303, etching the first mask layer 169 and the second metal layer 166using the first mask layer 169 as a mask to obtain a plurality oftriangular prism structures 167;

S304, etching the isolation layer 164 using the plurality of triangularprism structures 167 as a mask to obtain a plurality of secondrectangular structures 165;

S305, etching the first metal layer 162 using the plurality of secondrectangular structures 165 as a mask to obtain a plurality of firstrectangular structures 163; and

S306, removing the first mask layer 169 to obtain the plurality ofthree-dimensional nanostructures 161.

In step S301, the first metal layer 162 is deposited on the secondsemiconductor layer 140, and the second metal layer 166 is deposited onthe isolation layer 164. The method of depositing the first metal layer162 and the second metal layer 166 can be electron beam evaporationmethod or ion sputtering method. The material of the first metal layer162 and the second metal layer 166 can be metals with surface plasmonpolaritons, such as gold, silver, copper, and aluminum. In one exemplaryembodiment, the material of the first metal layer 162 and the secondmetal layer 166 is gold. The thickness of the first metal layer 162 isin a range of 20 nanometers to 500 nanometers. Furthermore, thethickness of the first metal layer 162 can be in a range of 50nanometers to 200 nanometers. In one exemplary embodiment, the thicknessof the first metal layer 162 is 100 nanometers. The thickness of thesecond metal layer 166 should be greater than 40 nanometers so that thesecond metal layer 166 can be a free-standing structure after removingthe first mask layer 169. The free-standing structure is that the secondmetal layer 166 can keep a certain shape without any supporter. Thethickness of the second metal layer 166 can be in a range of 40nanometers to 800 nanometers. Furthermore, the thickness of the secondmetal layer 166 can be in a range of 130 nanometers to 400 nanometers.In one exemplary embodiment, the thickness of the second metal layer 166is 200 nanometers.

The isolation layer 164 is used to isolate the first metal layer 162 andthe second metal layer 166, thus the first metal layer 162 is notdestroyed when the second metal layer 166 is etched. When the materialof the first metal layer 162 is different from the material of thesecond metal layer 166, the isolation layer 164 can be omitted. Thematerial of the isolation layer 164 can be metal or metal oxide, such aschromium, tantalum, tantalum oxide, titanium dioxide, silicon, orsilicon dioxide. The thickness of the isolation layer 164 can be in arange of 5 nanometers to 100 nanometers. Furthermore, the thickness ofthe isolation layer 164 can be in a range of 5 nanometers to 60nanometers. When the material of the isolation layer 164 is metal, thematerial of the isolation layer 164 should be different from thematerial of the first metal layer 162 and the second metal layer 166. Inone exemplary embodiment, the material of the isolation layer 164 ischromium, and the thickness of the isolation layer 164 is 10 nanometers.

In step S302, the method for making the first mask layer 169 can beoptical etching method, plasma etching method, electron beam etchingmethod, focused ion beam etching method, hot embossing method, ornanoimprinting method. In one exemplary embodiment, the first mask layer169 is formed on the second metal layer 166 by nanoimprinting method.Compared with other methods, the nanoimprinting method for making thefirst mask layer 169 has a plurality of advantages, such as highprecision, high efficiency, low energy consumption, low temperatureoperation, and low cost. The first mask layer 169 includes a pluralityof bodies 1694, and the body 1694 defines a plurality of fourth openings1692 parallel with and spaced from each other. The plurality of fourthopenings 1692 can be strip openings or square openings. In one exemplaryembodiment, the plurality of fourth openings 1692 are strip openings,each fourth opening 1692 extends to two opposite edges of the first masklayer 169. Each adjacent body 1694 and fourth opening 1692 is defined asa period. The width of the period is in a range of 90 nanometers to 1000nanometers. Furthermore, the width of the period is in a range of 121nanometers to 650 nanometers. The width of each fourth opening 1692 canbe equal to the width of each body 1694. The width of each fourthopening 1692 and the width of each body 1694 can also be different. Thewidth of each fourth opening 1692 is in a range of 40 nanometers to 450nanometers. The width of each body 1694 is in a range of 50 nanometersto 450 nanometers. In one exemplary embodiment, the width of the periodis 200 nanometers, the width of each fourth opening 1692 is 100nanometers. The height of the body 1694 is in a range of 10 nanometersto 1000 nanometers. Furthermore, the height of the body 1694 is in arange of 20 nanometers to 800 nanometers. Furthermore, the height of thebody 1694 is in a range of 30 nanometers to 700 nanometers. In oneexemplary embodiment, the height of the body 1694 is 200 nanometers.

In step S303, the structure obtained after the step S302 is placed in areactive plasma system for etching, thus a plurality of parallel andspaced triangular prism structures 167 are obtained, the plurality oftriangular prism structures 167 are arranged. The etching gas in theetching system is a mixed gas of a physical etching gas and a reactiveetching gas. The physical etching gas can be argon gas, or helium, andthe reactive etching gas can be oxygen gas, chlorine, boron trichloride,or tetrachloride carbon. The physical etching gas and the reactiveetching gas can be selected according to the material of the secondmetal layer 166 and the first mask layer 169 so that the etching gas hasa higher etching rate. For example, when the material of the secondmetal layer 166 is gold, platinum, or palladium, the physical etchinggas is argon gas. When the material of the second metal layer 166 iscopper, the physical etching gas is helium. When the material of thesecond metal layer 166 is aluminum, the physical etching gas is argongas. In one exemplary embodiment, the physical etching gas is argon gas,and the reactive etching gas is oxygen gas.

The physical etching gas and the reactive etching gas are introducedinto the etching system. On the one hand, the body 1694 of the firstmask layer 169 is progressively etched by the reactive etching gas; onthe other hand, the exposed second metal layer 166 can also be etched bythe physical etching gas. As the first mask layer 169 is progressivelyetched, the width of the fourth opening 1692 gradually becomes greater.Since the exposed part of the second metal layer 166 corresponds to thefourth opening 1692, the etching width of the exposed part graduallybecomes greater from bottom to top. The first mask layer 169 can beremoved or partially removed by the reactive etching gas. The exposedpart of the second metal layer 166 can be removed or partially removedby the physical etching gas. The ratio between the horizontal etchingrate and the vertical etching rate can be selected by adjusting therelationship of volumetric flow, pressure and power of argon gas andoxygen gas. The triangular prism structures 167 can be obtained byadjusting the ratio. The second metal layer 166 defines a plurality ofparallel and spaced third openings 1662 and comprises a plurality oftriangular prism structures 167. The isolation layer 164 is exposedthrough the third openings 1662.

In step S304, a plurality of parallel and spaced second rectangularstructures 165 can be obtained by etching the isolation layer 164. Inone exemplary embodiment, the material of the isolation layer 164 ischromium, the etching gas is a mixed gas of oxygen gas and chlorine gas.

The isolation layer 164 defines a plurality of parallel and spacedsecond openings 1642 and comprises a plurality of second rectangularstructures 165. The second openings 1642 is stripe shaped. The secondopenings 1642 correspond to the third openings 1662, and the secondrectangular structures 165 correspond to the triangular prism structures167. The first metal layer 162 is exposed through the second openings1642.

In step S305, a plurality of parallel and spaced first rectangularstructures 163 can be obtained by etching the first metal layer 162.

The physical etching gas and the reactive etching gas are introducedinto the etching system. The physical etching gas is argon gas, and thereactive etching gas is a mixture of chlorine gas and oxygen gas. Thephysical etching gas and the reactive etching gas simultaneously etchthe first metal layer 162.

A plurality of first openings 1622 are obtained by etching a part of thefirst metal layer 162 corresponding to the second openings 1642. Inaddition, some metal particles or powders can be produced and fall offfrom the first metal layer 162 during the etching process. If there isno reactive etching gas, the metal particles or powders will accumulatealong the sidewalls of the first openings 1622 to form a thick edge, andthat will also result in a large surface roughness of the sidewalls ofthe first openings 1622. A gradient of the etching rate of the firstmetal layer 162 along each direction tends to be stable. Since the metalparticles or powders are deposited on the bottom surfaces of the firstopenings 1622, the accumulation of the metal particles or powders on thebottom surfaces of the first openings 1622 is equal to a reduction inthe vertical etching rate and also equal to an increase in thehorizontal etching rate. The excess metal particles or powders depositedon the sidewalls of the first openings 1622 can be etched by thereactive etching gas and the physical etching gas. The first rectangularstructures 163 have a regular structure and a small surface roughness.

The shape of the first openings 1622 is regular rectangle after the stepS305 being completed. The width of the first openings 1622 is in a rangeof 10 nanometers to 350 nanometers. The width of the first openings 1622can be controlled by adjusting the etching time. The thickness of thefirst rectangular structures 163 can be controlled by adjusting theetching time. In one exemplary embodiment, the width of the firstopenings 1622 is 160 nanometers.

In step S306, the residual photoresist remains in the structure obtainedby step S305. The plurality of three-dimensional nanostructures 161 areobtained by removing the residual photoresist. The residual photoresistcan be resolved by dissolving agent. The dissolving agent can betetrahydrofuran (THF), acetone, butanone, cyclohexane, n-hexane,methanol, absolute ethanol, or non-toxic or low toxicity ofenvironmentally friendly solvents. In one exemplary embodiment, theresidual photoresist is removed by ultrasonic cleaning in acetonesolution. FIG. 7 and FIG. 8 are SEM images of the plurality ofthree-dimensional nanostructures 161.

In step S40, the substrate 100 can be removed by methods of laserirradiating, corroding, and self stripping by temperature differences.The removal method can be selected according to the material of thesubstrate 100 and the first semiconductor layer 120. In one exemplaryembodiment, the substrate 100 is removed by laser irradiating method.The wavelength of the laser can be selected according to the material ofthe first semiconductor layer 120 and the substrate 100. An energy ofthe laser is smaller than a band gap energy of the substrate 100 andgreater than the band gap energy of the first semiconductor layer 120.The laser can access the substrate 100 and reach the first semiconductorlayer 120 to make the substrate 100 be stripped from the firstsemiconductor layer 120. The buffer layer 110 has a strong laserabsorption which results in the rapidly increasing temperature, therebydecomposing the buffer layer 110.

In step S50, the first electrode 180 can be an N-type electrode or aP-type electrode which is consistent with the first semiconductor layer120. The second electrode 182 can be an N-type electrode or a P-typeelectrode which is consistent with the second semiconductor layer 140.The second electrode 182 is located on the second area 1404 of thesecond semiconductor layer 140. A material of the first electrode 180and the second electrode 182 can be the same, such as titanium (Ti),silver (Ag), aluminum (Al), nickel (Ni), gold (Au) or an alloy thereof.In one exemplary embodiment, the first electrode 180 is an N-typeelectrode, the second electrode 182 is a P-type electrode.

The first electrode 180 is located on the first semiconductor layer 120,so that the current in the light emitting diode 10 propagates in adirection perpendicular to the source layer. Thus, the light emittingdiode 10 forms a light emitting diode with a vertical structure.

In an operation of the light emitting diode 10, a voltage is applied tothe first semiconductor layer 120 via the first electrode 180 and thesecond semiconductor layer 140 via the second electrode 182. The photonsare then generated from the active layer 130 and as the near fieldevanescent waves reaches the metallic plasma generating layer 160. Themetallic plasma is then generated from the metallic plasma generatinglayer 160, spreads around, and coupled into an emergent light emittedout. This process can increase the light extraction efficiency of thelight emitting diode 10. In the process, the quantum well effect betweenthe metallic plasma and the active layer 130 can cause the active layer130 to produce more photons and the produced photons arrive at themetallic plasma generating layer 160 to produce more metallic plasma.Therefore, a luminous efficiency of the light emitting diode 10 can beincreased.

In addition, the photons are incident on the three-dimensionalnanostructures with a large angle, the extracting angle of the photonscan be changed to make the photons emit from a light exit surface. Thus,the light extraction efficiency of the light emitting diode 10 can beincreased. The three-dimensional nanostructures increase the light exitarea, much scattering happens on the metallic plasma generating layer160. Thus, the metal plasma cam be more easily released from themetallic plasma generating layer 160. The luminous efficiency of thelight emitting diode 10 can be increased.

Referring to FIG. 9, an embodiment of a light emitting diode 20comprises a first semiconductor layer 120, an active layer 130, a secondsemiconductor layer 140, a metallic plasma generating layer 260, a firstelectrode 180, and a second electrode 182. The first semiconductor layer120, the active layer 130, and the second semiconductor layer 140 arestacked in that order. A surface of the second semiconductor layer 140defines a first area 1402 and a second area 1404. The metallic plasmagenerating layer 260 is located on the first area 1402. The firstelectrode 180 is electrically connected to the first semiconductor layer120. The second electrode 182 is located on the second area 1404 andelectrically connected to the second semiconductor layer 140. Themetallic plasma generating layer 260 includes a plurality ofthree-dimensional nanostructures 261. The three-dimensionalnanostructures 261 comprises a first rectangular structure 163 and atriangular prism structure 167. The first rectangular structure 163 islocated on the first area 1402. The triangular prism structure 167 islocated on the first rectangular structure 163. The width of a bottomsurface of the triangular prism structure 167 is greater than the widthof a top surface of the first rectangular structure 163. The materialsof the first rectangular structure 163 and the triangular prismstructure 167 are both metal materials. The material of the firstrectangular structure 163 is different from that of the triangular prismstructure 167.

The light emitting diode 20 is similar to the light emitting diode 10except that the three-dimensional nanostructures 261 of the metallicplasma generating layer 260 only consists of the first rectangularstructure 163 and the triangular prism structure 167.

Referring to FIG. 10, an embodiment of a light emitting diode 30comprises a first semiconductor layer 120, an active layer 130, a secondsemiconductor layer 140, a metallic plasma generating layer 160, a firstoptical symmetric layer 150, a second optical symmetric layer 170, afirst electrode 180, and a second electrode 182. The first semiconductorlayer 120, the active layer 130, and the second semiconductor layer 140are stacked in that order. A surface of the second semiconductor layer140 defines a first area 1402 and a second area 1404. The firstelectrode 180 is electrically connected to the first semiconductor layer120. The second electrode 182 is located on the second area 1404 andelectrically connected to the second semiconductor layer 140. The firstoptical symmetric layer 150 is located on the first area 1402. Themetallic plasma generating layer 160 is located on the first opticalsymmetric layer 150. The second optical symmetric layer 170 is locatedon the metallic plasma generating layer 160. The metallic plasmagenerating layer 160 includes a plurality of three-dimensionalnanostructures 161. The three-dimensional nanostructures 161 comprises afirst rectangular structure 163, a second rectangular structure 165, anda triangular prism structure 167. The first rectangular structure 163 islocated on the first optical symmetric layer 150. The second rectangularstructure 165 is located on the first rectangular structure 163. Thetriangular prism structure 167 is located on the second rectangularstructure 165. The width of a bottom surface of the triangular prismstructure 167 is equal to the width of a top surface of the secondrectangular structure 165, and is greater than the width of a topsurface of the first rectangular structure 163. The materials of thefirst rectangular structure 163 and the triangular prism structure 167are both metal materials.

The light emitting diode 30 is similar to the light emitting diode 10except that the light emitting diode 30 further includes the firstoptical symmetric layer 150 and the second optical symmetric layer 170.Selectively, the second optical symmetric layer 170 can also be removed.

A difference between a refractive index of the first optical symmetriclayer 150 and an equivalent refractive index of the source layer issmaller than or equal to 0.3.

A refractive index of the second optical symmetric layer 170 is similarto an equivalent refractive index of the first semiconductor layer 120,the active layer 130, the second semiconductor layer 140, and the firstoptical symmetric layer 150. A difference between the refractive indexof the second optical symmetric layer 170 and the equivalent refractiveindex of the first semiconductor layer 120, the active layer 130, thesecond semiconductor layer 140, and the first optical symmetric layer150 is smaller than or equal to 0.5. The luminous efficiency of thelight emitting diode 20 is high.

The light emitting diode 30 is an optical symmetric structure with themetallic plasma generating layer 160 as an optical symmetric center. Theoptical symmetric structure refers to two components in the opticalsymmetric position which have a close refractive index. Thus, the lightgenerated in the active layer 130 is evenly emitted from the firstsemiconductor layer 120 and the first optical symmetric layer 150.

Referring to FIG. 11 and FIG. 12, an embodiment of a light emittingdiode 40 comprises a first semiconductor layer 120, an active layer 130,a second semiconductor layer 140, a metallic plasma generating layer160, a first electrode 180, and a second electrode 182. The firstsemiconductor layer 120, the active layer 130, and the secondsemiconductor layer 140 are stacked in that order. The first electrode180 is electrically connected to the first semiconductor layer 120. Themetallic plasma generating layer 160 is located on the secondsemiconductor layer 140. The second electrode 182 is located on themetallic plasma generating layer 160. The metallic plasma generatinglayer 160 includes a plurality of three-dimensional nanostructures 161.The three-dimensional nanostructures 161 comprises a first rectangularstructure 163, a second rectangular structure 165, and a triangularprism structure 167. The first rectangular structure 163 is located onthe second semiconductor layer 140. The second rectangular structure 165is located on the first rectangular structure 163. The triangular prismstructure 167 is located on the second rectangular structure 165. Thewidth of a bottom surface of the triangular prism structure 167 is equalto the width of a top surface of the second rectangular structure 165,and is greater than the width of a top surface of the first rectangularstructure 163. The materials of the first rectangular structure 163 andthe triangular prism structure 167 are both metal materials.

The light emitting diode 40 is similar to the light emitting diode 10except that the second electrode 182 of the light emitting diode 40 islocated on a surface of the metallic plasma generating layer 160 awayfrom the second semiconductor layer 140. The second electrode 182between adjacent three-dimensional nanostructures 161 is suspended. Thesecond electrode 182 can be a free-standing metal sheet or a carbonnanotube structure. The current injected into the second semiconductorlayer 140 is uniform through the three-dimensional nanostructures 161.The material of the second rectangular structure 165 is metal orsemiconductor. Selectively, the second rectangular structure 165 canalso be removed.

The second electrode 182 can be disposed at one end of the metallicplasma generating layer 160, or an intermediate region of the metallicplasma generating layer 160. The second electrode 182 is electricallyconnected to the metallic plasma generating layer 160.

Referring to FIG. 13 and FIG. 14, an embodiment of a light emittingdiode 50 comprises a first semiconductor layer 120, an active layer 130,a second semiconductor layer 140, a metallic plasma generating layer160, a first electrode 180, and a second electrode 182. The firstsemiconductor layer 120, the active layer 130, and the secondsemiconductor layer 140 are stacked in that order. The first electrode180 is electrically connected to the first semiconductor layer 120. Themetallic plasma generating layer 160 is located on the secondsemiconductor layer 140. The second electrode 182 is located on themetallic plasma generating layer 160. The metallic plasma generatinglayer 160 includes a plurality of three-dimensional nanostructures 161.The three-dimensional nanostructure 161 comprises a first rectangularstructure 163, a second rectangular structure 165, and a triangularprism structure 167. The first rectangular structure 163 is located onthe second semiconductor layer 140. The second rectangular structure 165is located on the first rectangular structure 163. The triangular prismstructure 167 is located on the second rectangular structure 165. Thewidth of a bottom surface of the triangular prism structure 167 is equalto the width of a top surface of the second rectangular structure 165,and is greater than the width of a top surface of the first rectangularstructure 163. The materials of the first rectangular structure 163 andthe triangular prism structure 167 are both metal materials.

The method of making the second electrode 182 can include the followingmethods:

first method, depositing the second electrode 182 on the metallic plasmagenerating layer 160 to cover the plurality of three-dimensionalnanostructures 161 and gaps between adjacent three-dimensionalnanostructures;

second method, defining a third area and a fourth area on the secondsemiconductor layer 140, forming the metallic plasma generating layer160 on the third area, forming the second electrode 182 on the fourtharea, wherein a direction of the second electrode 182 intersects withthe direction of the plurality of three-dimensional nanostructures 161,and the second electrode 182 is electrically connected to the pluralityof three-dimensional nanostructures 161.

third method, referring to FIG. 6 and FIG. 15, defining a fifth area1664 and a sixth area 1666 on the second metal layer 166, forming themetallic plasma generating layer 160 on the sixth area 1666, forming thesecond electrode 182 on the fifth area 1664, wherein a direction of thesecond electrode 182 intersects with the direction of the plurality ofthree-dimensional nanostructures 161, the second electrode 182 and theplurality of three-dimensional nanostructures 161 are an integratedstructure. When the first mask layer 169 is etched, the sixth area 1666is not etched.

The second electrode 182 can be disposed at one end of the metallicplasma generating layer 160, or an intermediate region of the metallicplasma generating layer 160. The second electrode 182 is electricallyconnected to the metallic plasma generating layer 160.

When the material of the second rectangular structure 165 is insulatingmaterials, the first method and the second method are suitable formaking the second electrode 182. When the material of the secondrectangular structure 165 is metal or semiconductor, or thethree-dimensional nanostructure 161 does not inlcude the secondrectangular structure 165, the third method is applicable.

The light emitting diode 50 is similar to the light emitting diode 10except that the second electrode 182 of the light emitting diode 50intersects with the plurality of three-dimensional nanostructures 161.The second electrode 182 is in contact with each layer of thethree-dimensional nanostructure 161. Thus, the second electrode 182 iselectrically connected to the plurality of three-dimensionalnanostructures 161. The current injected into the second semiconductorlayer 140 is uniform through the three-dimensional nanostructures 161.

At least one of the first electrode 181 and the second electrode 182 isa light transmitting layer, so that the transmitting electrode can be alight emitting surface of the light emitting diode 50. When the firstelectrode 181 is a light emitting layer and the second electrode 182 isa light reflecting layer, the first electrode 181 is a light emittingsurface. When the first electrode 181 is a light reflecting layer andthe second electrode 182 is a light emitting layer, the light emittinglayer has a plurality of grooves, the exit angle can be changed due torefraction, and the light emitting rate of the light emitting diode 50is improved.

Referring to FIG. 16, an embodiment of a light emitting diode 60comprises a substrate 100, a buffer layer 110, a first semiconductorlayer 120, an active layer 130, a second semiconductor layer 140, ametallic plasma generating layer 160, a first electrode 180, and asecond electrode 182. The substrate 100, the buffer layer 110, the firstsemiconductor layer 120, the active layer 130, and the secondsemiconductor layer 140 are stacked in that order. A surface of thesecond semiconductor layer 140 defines a first area 1402 and a secondarea 1404. The metallic plasma generating layer 160 is located on thefirst area 1402. The first electrode 180 is electrically connected tothe first semiconductor layer 120. The second electrode 182 is locatedon the second area 1404 and electrically connected to the secondsemiconductor layer 140. The second electrode 182 and the firstelectrode 180 are disposed on the same side of the first semiconductorlayer 120. The metallic plasma generating layer 160 includes a pluralityof three-dimensional nanostructures 161. The three-dimensionalnanostructure 161 comprises a first rectangular structure 163, a secondrectangular structure 165, and a triangular prism structure 167. Thefirst rectangular structure 163 is located on the second semiconductorlayer 140. The second rectangular structure 165 is located on the firstrectangular structure 163. The triangular prism structure 167 is locatedon the second rectangular structure 165. The width of a bottom surfaceof the triangular prism structure 167 is equal to the width of a topsurface of the second rectangular structure 165, and is greater than thewidth of a top surface of the first rectangular structure 163. Thematerials of the first rectangular structure 163 and the triangularprism structure 167 are both metal materials.

The light emitting diode 60 is similar to the light emitting diode 10except that the second electrode 182 and the first electrode 180 aredisposed on the same side of the first semiconductor layer 120. Thecurrent generated by the first electrode 180 and the second electrode182 is laterally conducted in the second semiconductor layer 140 havinghigh resistance. The buffer layer 110 is an optional structure.

The light emitting diode of the disclosure has many advantages. Firstly,the metallic plasma generating layer includes a plurality ofthree-dimensional nanostructures, gaps between adjacentthree-dimensional nanostructures can increase the light transmittance.Secondly, the three-dimensional nanostructure consists of at least twoparts of metal having surface plasmons, and the three-layer structurecascades to achieve field enhancement; the photons are then generatedfrom the active layer and as the near field evanescent waves reaches themetallic plasma generating layer; the metallic plasma is then generatedfrom the metallic plasma generating layer, spreads around, and coupledinto an emergent light emitted out. Thirdly, the light emitting diodecan further include a first optical symmetric layer and a second opticalsymmetric layer to make that the metallic plasma generating layer is anoptical symmetric center of the light emitting diode; two components inthe optical symmetric position have a close refractive index, thus, thelight generated in the active layer is evenly emitted from the firstsemiconductor layer and the first optical symmetric layer.

The embodiments shown and described above are only examples. Even thoughnumerous characteristics and advantages of the present technology havebeen set forth in the foregoing description, together with details ofthe structure and function of the present disclosure, the disclosure isillustrative only, and changes may be made in the detail, including inmatters of shape, size, and arrangement of the parts within theprinciples of the present disclosure up to, and including, the fullextent established by the broad general meaning of the terms used in theclaims.

Depending on the embodiment, certain of the steps of methods describedmay be removed, others may be added, and the sequence of steps may bealtered. The description and the claims drawn to a method may comprisesome indication in reference to certain steps. However, the indicationused is only to be viewed for identification purposes and not as asuggestion as to an order for the steps.

What is claimed is:
 1. A light emitting diode, the light emitting diodecomprising: a first semiconductor layer, an active layer, a secondsemiconductor layer, wherein the first semiconductor layer, the activelayer, and the second semiconductor layer are sequentially stacked witheach other, a surface of the second semiconductor layer defines a firstarea; a metallic plasma generating layer, located on the secondsemiconductor layer; a first electrode, electrically connected to thefirst semiconductor layer; and a second electrode, electricallyconnected to the second semiconductor layer; wherein the metallic plasmagenerating layer comprises a plurality of three-dimensionalnanostructures, the three-dimensional nanostructure comprises a firstrectangular structure, a second rectangular structure, and a triangularprism structure, the first rectangular structure is located on the firstarea, the second rectangular structure is located on the firstrectangular structure, the triangular prism structure is located on thesecond rectangular structure, the width of a bottom surface of thetriangular prism structure is equal to the width of a top surface of thesecond rectangular structure, and is greater than the width of a topsurface of the first rectangular structure, the first rectangularstructure is a first metal layer, and the triangular prism structure isa second metal layer.
 2. The light emitting diode as claimed in claim 1,wherein a first material of the first metal layer is selected from thegroup consisting of gold, silver, copper, and aluminum, and a secondmaterial of the second metal layer is selected from the group consistingof gold, silver, copper, and aluminum.
 3. The light emitting diode asclaimed in claim 1, wherein a material of the second rectangularstructure is selected from the group consisting of chromium, thalliumpentoxide, titanium dioxide, silicon, and silica.
 4. The light emittingdiode as claimed in claim 1, wherein a distance between the two adjacentthree-dimensional nanostructures is in a range of 40 nanometers to 450nanometers.
 5. The light emitting diode as claimed in claim 1, wherein afirst thickness of the first rectangular structure is in a range of 20nanometers to 500 nanometers, a second thickness of the secondrectangular structure is in a range of 5 nanometers to 100 nanometers,and a third thickness of the triangular prism structure is in a range of40 nanometers to 800 nanometers.
 6. The light emitting diode as claimedin claim 1, wherein the second electrode intersects with the pluralityof three-dimensional nanostructures, the second electrode iselectrically connected to each three-dimensional nanostructure.
 7. Thelight emitting diode as claimed in claim 6, wherein the second electrodeis located on a side of the plurality of three-dimensionalnanostructures away from the second semiconductor layer.
 8. The lightemitting diode as claimed in claim 7, wherein the second electrodefurther fills gaps between adjacent three-dimensional nanostructures. 9.The light emitting diode as claimed in claim 8, wherein the secondelectrode and the plurality of three-dimensional nanostructures areintegrated.
 10. A light emitting diode, the light emitting diodecomprising: a first semiconductor layer, an active layer, a secondsemiconductor layer, wherein the first semiconductor layer, the activelayer, and the second semiconductor layer are sequentially stacked witheach other, a surface of the second semiconductor layer defines a firstarea; a metallic plasma generating layer, located on the secondsemiconductor layer; a first electrode, electrically connected to thefirst semiconductor layer; and a second electrode, electricallyconnected to the second semiconductor layer; wherein the metallic plasmagenerating layer comprises a plurality of three-dimensionalnanostructures, the three-dimensional nanostructure comprises arectangular structure, and a triangular prism structure, the rectangularstructure is located on the first area, the triangular prism structureis located on the rectangular structure, the width of a bottom surfaceof the triangular prism structure is greater than the width of a topsurface of the rectangular structure, the rectangular structure is afirst metal layer, and the triangular prism structure is a second metallayer, the first metal layer and the second metal layer are different.11. The light emitting diode as claimed in claim 10, wherein materialsof the first metal layer and the second metal layer are selected fromthe group consisting of gold, silver, copper, and aluminum.
 12. Thelight emitting diode as claimed in claim 10, wherein the secondelectrode intersects with the plurality of three-dimensionalnanostructures, the second electrode is electrically connected to eachthree-dimensional nanostructure.
 13. The light emitting diode as claimedin claim 12, wherein the second electrode is located on a side of theplurality of three-dimensional nanostructures away from the secondsemiconductor layer.
 14. The light emitting diode as claimed in claim13, wherein the second electrode further fills gaps between adjacentthree-dimensional nanostructures.
 15. The light emitting diode asclaimed in claim 14, wherein the second electrode and the plurality ofthree-dimensional nanostructures are integrated.